Conventionally, there has been proposed the use of a carbon membrane excellent in thermal resistance and chemical stability as a separation membrane for separating specific gas or the like from a mixture of various gases or the like, or as a separation membrane for separating a specific component from a mixed liquid or an aqueous solution of various organic solvent such as alcohol from the viewpoint of environment and energy saving (see, e.g., Patent Documents 1 and 2).    Patent Document 1: JP-A-2003-286018    Patent Document 2: JP-A-2006-212480
When the carbon membrane was left at room temperature, water or the like was adsorbed to an oxygen contained functional group or the like slightly present on a carbon membrane surface to sometimes deteriorate permeation performance and separation performance of the carbon membrane. In contrast, the invention described in the Patent Document 1 tries to inhibit absorption of a water molecule and inhibit deterioration in permeation performance by subjecting a surface of the carbon membrane to a silylation treatment to impart hydrophobicity to the carbon membrane. Though the invention described in Patent Document 1 can effectively inhibit adsorption of a water molecule to the surface of the carbon membrane, the pore size of the carbon membrane is decreased by silylation, and as a result, the permeability rate falls off. Therefore, there is room to study further. In addition, the invention described in Patent Document 2 improves hydrophilicity of the membrane by immersing the carbon membrane in an acidic aqueous solution to allow a molecule of an acidic substance to be adsorbed, thereby improving selectivity of water in separation of water from an organic solvent such as water and alcohol. Though this particularly exhibits an effect in the case that the separation target is an organic solvent containing water, an effect against a mixed liquid of organic solvents or gas is uncertain. In addition, since an acidic substance such as acetic acid and hydrochloric acid is used, there are problems of odor, safety, and the like.